The present invention relates to a method and apparatus for helical filament winding operations, and more particularly relates to apparatus which may be used in such method, for wet and dry winding filament operations.
Filament winding which produces a high degree of fibre orientation is an extremely important industrial technique. Where glass fibre filaments are involved, filament winding produces a high degree of orientation and high glass loading to provide extremely high tensile strengths in the manufacture of hollow, generally cylindrical products such as chemical and fuel storage tanks, pipe, pressure vessels and rocket motor cases. In such industrial applications, special winding machines lay down continuous strands of glass or other reinforcement fibre which has been impregnated with a resin, in a predetermined pattern on an appropriately shaped mandrel, to provide maximum strength in the directions required. When sufficient layers of filament have been applied, the wound mandrel is then cured and the mandrel is then removed. Such filament wound products have the highest strength to weight ratio of any fibre reinforced plastic manufacturing process, and may be accurately machined.
In the present state of the art of helical filament winding over generally cylindrical mandrels, usually requires a filament source, a friction tensioner for the filament, a driven cam-follower guide and a driven winding mandrel. The drive rotates the mandrel which pulls the filament through the cam-follower guide which reciprocates tranversely in a direction parallel to the axis of rotation of the mandrel. U.S. Pat. No. 3,281,299 of Shobert issued Oct. 25, 1966 and U.S. Pat. No. 3,577,294 of David issued May 4, 1971 describe and illustrate examples of such filament winding setups. In present state of the art helical filament winding systems where the filament is wound over generally cylindrical mandrels, the winding ratio between mandrel rotations to traverse is critical to produce a uniform thickness. This ratio is generally locked in by utilizing either timing belt, gears, chains or electronic synchronization techniques. For a particular mandrel circumference, length and required helix angle of wind, the setup is unique. The winding ratio must be an exact non-integer to produce a progressively uniform windup by positioning generally multiple filaments alongside each other and preventing excessive buildup in some areas. The speeds of such operations are generally slow, and complex expensive apparatus is required.
Generally, the filament transverse feed guide is cam activated with a grooved moveable axially cam which itself must be driven to ensure proper transverse location of the guide at any particular time with respect to the filament being wound on the mandrel to ensure proper filament winding on the mandrel.
Other patents of general background interest include U.S. Pat. No. 3,025,205 of Young issued Mar. 13, 1962; U.S. Pat. No. 3,730,795 of Medney et al. issued May 1, 1973 and Canadian Pat. No. 943,931 of Stewart issued Mar. 19, 1974.
It is an object of the present invention to provide a simpler, more economical method and apparatus for guiding filament in helical filament winding operations. It is a further object of the present invention to provide such a guide which will enable high speed filament winding. Yet another object is to provide such a filament guide wherein the helical angle of the filament being wound is fixed solely by the configuration of the guide, and is independent of mandrel dimensions (diameter, length), thereby avoiding tedious setups between different sized mandrels.